Electronic automatic reset switch circuit and electronic keyboard musical instrument incorporating it

ABSTRACT

The electronic automatic reset switch circuit comprises a plurality of on-off switches each connected between ground and the set input of an associated reset-set flip-flop. The reset inputs of all flip-flops are interconnected and a diode is connected across the inputs of each flip-flop. Momentary closing of any switch grounds the reset output of the associated flipflop and that output remains grounded until another switch is closed. The musical instrument utilizes a plurality of electronic tone generators which feed an amplifier and speaker. A conventional typewriter keyboard is arranged so that certain keys, representing the melody to be played, work in conjunction with certain other keys, representing the chord to be played, and connected in the switch circuit above described so that in combination, the desired melody note and chord accompaniment are sounded together. Once a chord key is depressed, that chord continues to be utilized and sounded with additional melody notes even though the chord key has been released. This process will continue until another chord key is depressed. Circuitry is also provided for playing melody only. Music for the instrument is written as a succession of the alphabetic, numeric or punctuation signatures of the appropriate typewriter keys. The instrument is also provided with chord selector switches and a stepping sequence switch arranged so that chords in a musical composition can be set up in advance on the chord selector switches and played by key operation of the sequence switch.

United States Patent 1191 Herr 1 51 Nov. 5, 1974 Ernest A. Herr, 1850Rominger Rd., Winston-Salem, NC. 27107 [22] Filed: Nov. 14, 1973 [21]Appl. No.: 415,732

Related US. Application Data [63] Continuation-impart of Ser. No.349,233, April 9,

1973, abandoned.

[76] Inventor:

[52] 11.8. C1 84/1.01, 84/1.l7, 84/DIG. 22,

84/470, 35/5 [51] Int. Cl. Gl0h 1/00, GlOh 5/00 [58] Field of Search84/101, 1.03, 1.17, 1.24,

84/423-425, 433, 443, 470, DIG. 7, DIG. 22; 197/8; 35/5, 6

OTHER PUBLICATIONS John D. Lenk, Handbook of Logic Circuits, C. 1972, byReston Publishing Company, Inc., Reston, Virginia, p. 43.

RCA Transistor Manual, Copyright 1967, by Radio Corporation of America,p. 41 l.

Millman & Taube, Pulse, Digital, and Switching Waveforms, McGraw-l-lillBook Co., Copyright 1965,

I3 I30 13b 14 p i p Primary ExaminerRichard B. Wilkinson AssistantExaminerStanley J. Witkowski Attorney, Agent, or FirmBuell, Blenko &Ziesenheim [57] ABSTRACT The electronic automatic reset switch circuitcomprises a plurality of on-off switches each connected between groundand the set input of an associated reset-set flip-flop. The reset inputsof all flip-flops are interconnected and a diode is connected across theinputs of each flip-flop. Momentary closing of any switch grounds thereset output of the associated flipflop and that output remains groundeduntil another switch is closed.

The musical instrument utilizes a plurality of electronic tonegenerators which feed an amplifier and speaker. A conventionaltypewriter keyboard is arranged so that certain keys, representing themelody to be played, work in conjunction with certain other keys,representing the chord to be played, and connected in the switch circuitabove described so that in combination, the desired melody note andchord accompaniment are sounded together. Once a chord key is depressed,that chord continues to be utilized and sounded with additional melodynotes even though the chord key has been released. This process willcontinue until another chord key is depressed. Circuitry is alsoprovided for playing melody only. Music for the instrument is written asa succession of the alphabetic, numeric or punctuation signatures of theappropriate typewriter keys.

The instrument is also provided with chord selector switches and astepping sequence switch arranged so that chords in a musicalcomposition can be set up in advance on the chord selector switches andplayed by key operation of the sequence switch.

11 Claims, 10 Drawing Figures PATENIEDunv slam 38451684 sum 20; a

Ther ls A Tavern In The Town POLKA 'ernpo c Traditional MelodyInforhmtion CR V LR YRER'Q'FLR RR RR YRER K F R RQK HQ RO N2 0 l Y Yfiming Information Chordjnformation I Fig. 3.

ELECTRONIC AUTOMATIC RESET SWITCH CIRCUIT AND ELECTRONIC KEYBOARDMUSICAL INSTRUMENT INCORPORATING IT This application is acontinuation-in-part of my application Ser. No. 349,233, filed Apr. 9,I973, and now abandoned.

This invention relates to electronic keyboard musical instruments. It ismore particularly concerned with such an instrument which utilizes aconventional typewriter keyboard, of which certain keys trigger melodynotes and certain other keys trigger chords.

Electronic organs are well known. In a true organ each key triggers anelectronically generated tone which corresponds to one note, either of amelody or of a chord. Chords are played by depressing simultaneously thekeys corresponding to the notes in the chord. The sound is produced byone or more loud speakers into which the amplified outputs of the tonegenerators are fed.

Chord organs, so-called, are also known. In these, certain keys triggermulti-note chords. Thus, a melody is played by depressing sequentiallythe keys corresponding to the successive notes of the melody and theaccompaniment is played by depressing sequentially, in proper relationto the melody, the keys corresponding to the appropriate chords. Thechord sound, as well as the sound of a melody note, continues as long asthe appropriate key is depressed, and stops when the key is allowed torise.

Instruments of the types above described are conventionally providedwith keyboards quite similar to piano keyboards and are played in thesame way as a conventional piano or organ is played. The keys of some ofthese instruments are marked with the musical signature of the note orof the chord which they trigger. In either case, the ability to readmusic, in greater or less degree, is required of the performer, and themanual dexterity required is in greater or less degree that of a pianistor an organist. These skills are not possessed by many people who wouldlike to play a keyboard musical instrument and, therefore, represent abarrier to a wider enjoyment of such instruments.

It is an object of my invention to provide an electronic keyboardmusical instrument which can be readily played by those who cannot readmusic and by those who have no piano keyboard dexterity. It is anotherobject to provide an electronic keyboard instrument with both melody andchord keys marked with the markings of conventional typewriter keys. Itis another object to provide such an instrument in which music can beplayed in the same way a letter is typed on a typewriter. It is stillanother object to provide such instrument with means for selecting inadvance the chords to be played in a musical number and for playing theselected chords in selected order. It is yet another object to provideelectronic apparatus useful in electronic keyboard musical instrumentsand in other devices in which the operation of one key-actuated switchto the on" position automatically sets all other key-actuated switchesto the off" position. Other objects will appear in the course of thedescription of my invention which follows.

Without doubt the keyboard familiar to most individuals at the presenttime is the conventional typewriter keyboard and without doubt many morepeople can operate a typewriter in some fashion than can play the pianoor organ. My instrument to be described utilizes a conventionaltypewriter keyboard with conventional key markings. Certain keys areresponsible for supplying information that actuate electronic tonegenerators which generate single melody notes, a different note for eachsuch key. Certain other keys are responsible for supplying informationthat actuates electronic tone generators which generate multiple notechords, a different chord for each key. Music to be played on myinstrument is written as a succession of the alphabetic. numeric orpunctuation signatures which appear on conventional typewriter keyscorresponding in sequence to the notes of the melody and chords of theaccompaniment. It is played by depressing the various keys of thekeyboard in the sequence written, just as words are typed from copy on atypewriter.

An embodiment of my invention presently preferred by me is illustratedin the attached figures to which reference is now made.

FIG. 1 is a schematic diagram of my instrument illus- FIG. 3 is the samemelody as that of FIG. 2 written only in the keyboard notation formelody and accompaniment of my invention;

FIG. 4 is a typewriter keyboard suitable for my instrument;

FIGS. 5 through 9 are schematics of a pair of chord keys and certain oftheir associated circuits illustrating the way in which the actuation ofone chord key disables and resets a previously actuated chord key.

FIG. 10 is a schematic diagram of a modification of the apparatus ofFIG. I.

My embodiment comprehends means for producing a plurality of musicalnotes and a plurality of chords. Each chord comprises a plurality ofnotes, usually not more than four. I find that 22 melody notes and I2chords are adequate to recreate most popular music. I also provide meansfor playing melody unaccompanied, which means are actuated by athirteenth chord key. As each chord must be available in combinationwith each melody note the total number of circuits must be 13 times 22or 286. I further provide a plurality of manually operable selectorswitches each connected to each chord means and an electrically operatedsequence switch connected to the selector switches so that operation ofthe sequence switch plays the preselected chords in succession. I preferto use conventional npn transistor logic throughout.

My instrument (FIGS. 1 and 4) is provided with a plurality of melodykeys of which three are illustrated, designated 10, 10a and 10b, and aplurality of chord keys of which three are illustrated, designated 13,13a and 1312. As many melody keys and as many chord keys may be includedas are desired, but the circuits for each melody key are merelyduplicates of those for melody key 10 and the circuits of each chord aremerely duplicates of those for chord key 13. Only the circuits for thetwo prototype keys will here be described.

Melody key 10 comprises a grounded contact I! and a normally live orungrounded contact 12. Chord key 13 likewise comprises a groundedcontact 14 and a normally ungrounded contact 15. Contact 12 of melodykey is connected to one input 16 of a two-input nor gate 17. The otherinput 18 of gate 17 is connected with key 13 in a way to be described.As my apparatus comprehends l3 chords, contact 12 is also connected toone input each of 12 additional two-input nor gates corresponding to theremaining 12 chords. Three of these are shown as gates 17, 77 and 87.Other melody keys 10a and 10b comprise grounded contacts 110 and 11b,respectively, and ungrounded contacts 12a and 12b, respectively.Contacts 12a and 12b are connected to gates 17a, 77a and 87a and 17b,77b and 87b, respectively.

Ungrounded contact of chord key 13 is connected to the set input 21 of areset-set flip-flop memory circuit the reset output 22 of which isconnected to input 18 of two-input gate 17. The reset input 23 of memorycircuit 20 is connected to a busbar 33, which is common to the resetinputs of all the other memory circuits. Two of these are shown asmemory circuits 20a and 20b. A diode 34 has its positive lead connectedto reset input 23 and its negative terminal to set input 21 of memorycircuit 20.

Appropriate direct current operating voltage is also supplied totwo-input nor gate 17 and memory circuit 20 through conductors notshown. Output 19 of twoinput nor gate 17 is connected to the directcurrent operating voltage terminal 24 of chord composer 25. Chordcomposer is a buffered gate having four inputs, and an output terminal30. Each of the four inputs is connected to a separate tone generator26, 27, 28 and 29, respectively, which supplies a different frequency.The output of the chord composer is connected to the input of amplifier31 which in turn drives a loud speaker 32.

I have mentioned that my apparatus comprises 286 two-input nor gates 17.Each of these requires and is associated with a separate chord composer25. As my apparatus comprises thirteen different chords, a plurality oftone generators is required to supply the appropriate notes for eachchord to the group of 22 chord composers connected to each chord key.One of the keys 13 which I have denominated a chord key is a melodyonly, or chord by-pass key.

Although my apparatus may contain additional elements to be described,its overall operation will best be understood if the operation of thatmuch of it so far described is first explained.

The nor gates typified by gate 17 provide a positive output at outputterminal 19 only when both inputs l6 and 18 are grounded. The memorycircuits 20 are conventional flip-flops formed by two two-input andgates, the output of each being connected to an input terminal of theother. Understanding of the operation of memory circuits 20 will befacilitated by reference to FIGS. 5-9. Each of those figures shows twochord keys, l3 and 13a, with their associated memory circuits 20 and20a. The numerals in the blocks representing memory circuits 20 and 20aindicated symbolically the voltage at the adjoining terminal of thatcircuit at that step in the sequence of operating conditions to bedescribed. The chord keys l3 and 13a and their memory circuits 20 and20a are typical of any two chord keys and memory circuits of myinvention.

Those familiar with binary logic devices will recognize that thereset-set flip-flops and the two-input gates utilized in my apparatusrespond only to two levels of signal voltage-0 or l-and provide only thesame two levels of output. Hereinafter, I denominate a nominal 1 signalas positive and a nominal 0 signal as ground. I also denominate twosignal inputs or outputs which are both nominally 0 or nominally lsignals of the same character.

FIG. 5 illustrates the conditions obtaining when no chord key isdepressed and there is no output from speaker 32. Positive voltagesappear at inputs 21 and 23 of memory circuit 20 and at its reset output22. That output, which is connected to input nor 18 of two-input gate17, is effectively open circuited. The same conditions apply to memorycircuit 20a. When chord key 13 is depressed the conditions obtaining inthe two sets of circuits are then shown in FIG. 6. Input 21 of memorycircuit 20 is grounded, as is input 23 through diode 34. A positivevoltage still appears at output terminal 22. As all reset inputs 23,23a, etc. are connected by busbar 33, input 23a of memory circuit 20a isalso grounded. A positive voltage still appears on input terminal 21aand on output terminal 22a. Therefore, there is still no output fromspeaker 32.

When key 13 is released, however, the conditions are those shown in FIG.7. A positive voltage again appears on terminal 21 and, through diode34, on terminal 23. This results in ground condition at output terminal22. Input terminal 21a of memory 20a continues to show a positivevoltage, and the positive voltage now on busbar 33 appears on inputterminal 23a of memory circuit 20a. Its output terminal 22a thereforecontinues to show a positive voltage.

The ground condition at terminal 22 is applied to terminal 18 oftwo-input nor gate 17. A key 10 representing the first note of themelody is then depressed. This supplies ground directly to input 16 oftwo-input nor gate 17 and causes that gate to produce a positive directcurrent voltage at its output 19. Although memory circuit 20 suppliesground to the chord input terminal of 21 additional two-input gates andkey 10 supplies ground to the melody input terminal of 12 other twoinputgates, none of these will produce an output signal.

The output 19 of two-input nor gate 17 is adjusted to a value equal tothe operating voltage of chord composer 25. When this voltage is appliedto operating voltage terminal 24 of that chord composer, the lattercloses the circuits between the tone generator inputs 26, 27, 28 and 29and the output 30, and allows all those frequencies to be amplified byamplifier 31 and reproduced as music through loud speaker 32.

One of the notes of the chord will be that selected by melody key 10. Ifnow another melody key, 10a, is depressed, another two-input nor gate,17a, will be actuated, but it will only be one of the 22 strapped tomemory circuit 20 as has been mentioned. Therefore, the chord producedwill have the same three chord notes as that first produced but adifferent melody note.

A new chord is generated by depressing another chord key, such as 13a.The conditions with respect to keys l3 and 13a and their associatedmemory circuits 20 and 20a are then those shown in FIG. 8. Depressingkey 13a grounds input 21a of memory circuit 20a. Input terminal 23a isalso grounded through diode 34a, and this ground is extended by busbar33 to input terminal 23 of memory circuit 20. Output terminal 22 ofmemory circuit 20 is thus switched to a positive voltage, and the chordcorresponding to key 13 is cut off. Both inputs of memory circuit 20aare grounded and its reset output 22a is positive. The condition ofmemory circuits and 20a are the reverse of FIG. 6, and neither circuitproduces a chord. When key 13a is released, the conditions of memorycircuit 20 and 20a, shown in FIG. 9, are the reverse of those of FIG. 7,and the ground at output 22a of memory circuit 20a is supplied toterminal 78 of two-input nor gate 77. Gate 77v is identical to gate 17previously described.

It is evident, therefore, that the chord corresponding to key 13 willcontinue to be heard until another key, 13a, is depressed and released,and that operation resets memory circuit 20.

The thirteenth chord key previously mentioned which is depressed whenmelody only is to be played is connected to a memory circuit and aplurality of twoinput gates in the same way as the other chord keys. Thechord composers connected with the thirteenth chord key, however, areeach connected to a single tone generator only.

The remainder of the apparatus shown in FIG. 1 will now be described. Itprovides for the preselecting of the chords in a piece of music and theplaying of those chords in an automatic sequence. For this purpose myinstrument is provided with a plurality of manually operated selectorswitches, of which three are shown, designated 38, 38a and 38b. Thetotal number of selector switches 38 provided in an instrument should beat least equal to the number of successive chords in the accompanimentof the longest piece expected to be played on the instrument. As allselector switches are identical only switch 38 will be described indetail. It is a rotary switch having a plurality of circumferentiallyspaced contacts of which three are shown, designated 39, 40 and 41. Thenumber of such contacts is equal to the number of chords provided in theinstrument.

Switch 38 also has a rotary contact arm 42 which is movable manuallyinto successive conductive engagement with contacts 39, 40 and 41.Contact arm 42 is provided with a conducting lead-out terminal 43.Switch contact 39 is connected by conductor 66 and busbar 44 with livecontact 15 of chord key 13. Switch contact 40 is connected by conductor67 and busbar 45 with contact 15a of chord key 13a. Switch contact 41 isconnected with conductor 68 and busbar 46 with contact 15b of chord key13b. The corresponding contacts of the other switches 38a and 38b arelikewise connected with busbars 44, 4S and 46. Each switch also has azero position unconnected with any chord key.

My apparatus is also provided with an electrically operated sequenceswitch 48. This switch is a rotary tap stepping switch with spacedcircumferential contacts 49, 50 and 51. The number of those contactsequals the total number of selector switches 38 and the switch is alsoprovided with a zero position unconnected to any selector switch.Contact 49 is connected by conductor 52 to terminal 43 of selectorswitch 38. Contact 50 is connected by conductor 53 to terminal 43a ofselector switch 38a, and contact 51 is connected by conductor 54 toterminal 431) of selector switch 38b. Rotary contact arm 55 of sequenceswitch 48 is connected through conducting lead 56 to ground.

Contact arm 55 of sequence switch 48 is caused to rotate around theswitch circumference from one contact to the next in steps by aconventional solenoid rachet device 58. One terminal of the solenoid 58is connected by conductor 59 to ground and to a key 63 which I prefer tobe a typewriter space bar. The other end of the solenoid is connected byconductor 60 to one terminal of a source of power, such as a battery 61.The other terminal of battery 61 is connected by conductor 62 to livecontact 64 of key 63.

The switch apparatus above described is used in place of chord keys 13as may be desired. If the operator of the instrument wishes to use chordkeys 13 in the way which has been described he manually turns switch arm42 of the selector switch 38 to the zero position and does the same withthe arms of all the other selector switches. Those switches are, ofcourse, provided with knobs and face plates which indicate the chord keycorresponding to eachposition of the switch arm. Alternatively, theoperator can cause the contact arm 55 of sequence switch 48 to rotate toits zero position in the manner to be described. In either case, theconnection between the ground on'conductor 56 and live contacts 15, 15a,etc. of chord keys 13, 13a, etc. is broken.

If the operator wishes to use the switching apparatus he first turnscontact arm 42 of switch 38 to the contact corresponding to the firstchord of the composition to be played. In FIG. 1 that contact isindicated to be contact 41. He then turns contact arm 42a of switch 38ato the contact corresponding to the second chordcontact 39a. He turnscontact 42b of switch 38b to the contact corresponding to the thirdchord-contact 40b, and so on until every chord in the composition is setup on a selector switch. It is evident from FIG. 1 that the operationabove described connects arm 42 with contact 15b of key 13b throughconductors 68 and 46, arm 42a with contact 15 of key 13 throughconductors 66a and 44, and arm 42b with contact 15a of key 13a throughconductors 67b and 45, and the contact arms of the remaining selectorswitches with the live contacts of the appropriate chord keys. It is,therefore, only necessary to connect the contact arms of the selectorswitches successively to ground to cause those chords to be sounded insuccession.

This connection is accomplished by sequence switch 48. When key 63 isdepressed so as to make contact with live contact 64 current frombattery 64 flows through solenoid 58. The armature of the solenoid isattracted, operating the conventional stepping switch ratchet mechanismwhich moves contact arm 55 from the zero position to contact 49. Thisconnects arm 42 of selector switch 38 to ground through conductors 52and lead 56. The chord corresponding to chord key 13b is thus set up andis played when a melody key is depressed, in the way which has beendescribed. When the next chord is to be played the operator depresseskey 63 again, which brings about movement of arm 55 to the next contact50 in the way described, and so renders the next chord ready to beplayed. Thus, the operator, having selected the appropriate chords inadvance, need only depress key 63 momentarily at the proper time to havethe chord played.

FIG. 10 illustrates a modification of the apparatus of FIG. 1. Only onemelody key and one chord key and memory are shown. In the apparatus ofFIG. I as it has been described herein the melody key switch 10 whendepressed connects contact 12 to ground. In the modification of FIG. 10melody key 10 is connected to the positive terminal of voltage source75, such as a battery, the other terminal of which is grounded. Contact12 is connected to one input 16 of a two-input and gate 80. The otherinput 18 of that gate is connected to the set output 74 of memorycircuit 20. All other connections of the remaining memory circuits andgates remain unchanged.

The operation of chord key 13 and memory circuit 20 in the apparatus ofFIG. is the same as their operation in FIG. 1, which has been described.When melody key 10 of FIG. 10 is depressed, it connects the positivevoltage of source 75 to one input 16 of two-input and gate 80. Whenchord key 13 is depressed and released, the voltage at set output 74 ofmemory circuit is the opposite of that at terminal 22, that is to say itis a positive voltage, and that voltage is applied to the other input 18of and gate 80. And gate 80, therefore, produces a positive voltage atits output 19, and that voltage is applied to terminal 24 of chordcomposer as before.

The keys of my keyboard carry the markings of conventional typewriterkeys-letters, numbers and punctuation marks and are arranged in the sameway as a typewriter keyboard. I prefer to use the bottom row of thekeyboard, as far as possible, for my chord keys, 7

as shown in H0. 4. Music for my instrument is written as a sequence oftypewriter key markings or signatures, as may be seen in FlG. 2. Theletter C below the first note of the first line of music in that figureindicates the key for the initial chord, and the letter R is the initialmelody note. in the next bar the chord is changed to that represented bykey V. The melody is accompanied by that same chord throughout theremainder of the first line and the first three bars of the second line;in the fourth bar a new chord is played by depressing key B, and so on.The music is compactly written as a sequence of the characters, as isshown in FIG. 3. The chord keys are indicated as subscript charactersand timing information is conveyed by underlining the appropriate melodycharacters.

in the foregoing description I have referred to chord composer 25 as afour-input gate, but it is operated as a four-pole single throw relay.While I have described keys 10 and 13 as having one grounded contact, Iinclude under the term ground a busbar common to one contact of each keyand other points at ground potential, whether or not it is actuallygrounded. My apparatus is not, of course, limited to 22 melody keys and13 chord keys, but may comprise any number of either. It requires onlyone amplifier and one speaker, but two or more amplifiers and speakersmay be employed.

In the foregoing specification l have described a presently preferredembodiment of this invention; however, it will be understood that thisinvention can be otherwise embodied within the scope of the followingclaims.

' I claim:

' 1. Apparatus comprising a plurality of reset-set flipflops, an on-offswitch connected between ground and the set input of each flip-flop, areset bus bar connecting-the reset inputs of all the flip-flops, and adiode connected between the set and reset inputs of each flipflop withits positive terminal connected to the reset input, the on-off switchbeing a key operated chord switch, a plurality of key-operated melodynote on-off switches, a plurality of two-input gates equal to theproduct of the plurality of melody notes by the plurality of chords.each gate being adjusted to produce a positive output when both inputsignals are of the same character, means connecting each melody noteswitch between a signal source and one input of a plurality of thetwo-input gates equal to the number of chords,

' means connecting the output of each reset-set flip-flop having thesame character as the signal source with the other input of theplurality of the two-input gates equal to the number of melody notes, aplurality of multiinput chord composers equal to the plurality oftwoinput gates, each chord composer being connected to the output of asingle two-input gate and activated by the output from that gate toconnect the chord composers inputs with its output, a plurality of tonegenerators connected to the inputs of the chord composers, and meansconnecting the outputs of the chord composers with a sound-producingdevice.

2. Apparatus of claim 1 in which the chord composer is a multi-inputgate, each tone generator is connected to one input of that gate, andthe output from the twoinput gate connected to its melody note switchprovides the operating potential which opens the multi-input gate.

3. Apparatus of claim 1 including chord composers having a single tonegenerator each connected thereto.

4. Apparatus of claim 1 including a plurality of chord composers equalto the number of melody keys, each chord composer being connected to asingle tone generator.

5. Apparatus of claim 4 including a chord key and a reset-set flip-flopcircuit connected with each of the chord composers which is connected toa single tone generator.

6. Apparatus of claim 1 in which the keys operating the melody noteswitches and the keys operating the chord switches are arranged in theform of a typewriter keyboard.

7. Apparatus of claim 6 in which the keys carry distinguished indicia inthe form of typewriter characters and are arranged in the order of thecharacters of a typewriter keyboard.

8. Apparatus of claim 1 including a plurality of manually operableselector switches, each having a separate contact connected to eachchord switch, a multicontact sequence switch, means connecting the armof each selector switch to a separate contact of the sequence switch,means connecting the arm of the sequence switch to ground, andelectrical means including an on-off switch for operating the sequenceswitch.

9. Apparatus of claim 8 in which the keys operating the melody noteswitches and the keys operating the chord switches are arranged in theform of a typewriter keyboard and the switch for operating the sequenceswitch is operated by the space bar of the typewriter keyboard.

10. Apparatus of claim 1 in which the signal source for the melody noteswitches is ground, the two-input gates are nor gates, and the resetoutput of each resetset flip-flop is connected with the other input ofthe plurality of two-input gates equal to the number of melody notes.

11. Apparatus of claim 1 in which the signal source for the melody noteswitches is a voltage source, the twoinput gates are and gates, and theset output of each resetset flip-flop is connected with the other inputof the plurality of two-input gates equal to the number of melody notes.

h i i i

1. Apparatus comprising a plurality of reset-set flip-flops, an on-offswitch connected between ground and the set input of each flip-flop, areset bus bar connecting the reset inputs of all the flip-flops, and adiode connected between the set and reset inputs of each flip-flop withits positive terminal connected to the reset input, the on-off switchbeing a key operated chord switch, a plurality of key-operated melodynote on-off switches, a plurality of two-input gates equal to theproduct of the plurality of melody notes by the plurality of chords,each gate being adjusted to produce a positive output when both inputsignals are of the same character, means connecting each melody noteswitch between a signal source and one input of a plurality of thetwo-input gates equal to the number of chords, means connecting theoutput of each reset-set flip-flop having the same character as thesignal source with the other input of the plurality of the two-inputgates equal to the number of melody notes, a plurality of multi-inputchord composers equal to the plurality of two-input gates, each chordcomposer being connected to the output of a singlE two-input gate andactivated by the output from that gate to connect the chord composer''sinputs with its output, a plurality of tone generators connected to theinputs of the chord composers, and means connecting the outputs of thechord composers with a sound-producing device.
 2. Apparatus of claim 1in which the chord composer is a multi-input gate, each tone generatoris connected to one input of that gate, and the output from thetwo-input gate connected to its melody note switch provides theoperating potential which opens the multi-input gate.
 3. Apparatus ofclaim 1 including chord composers having a single tone generator eachconnected thereto.
 4. Apparatus of claim 1 including a plurality ofchord composers equal to the number of melody keys, each chord composerbeing connected to a single tone generator.
 5. Apparatus of claim 4including a chord key and a reset-set flip-flop circuit connected witheach of the chord composers which is connected to a single tonegenerator.
 6. Apparatus of claim 1 in which the keys operating themelody note switches and the keys operating the chord switches arearranged in the form of a typewriter keyboard.
 7. Apparatus of claim 6in which the keys carry distinguished indicia in the form of typewritercharacters and are arranged in the order of the characters of atypewriter keyboard.
 8. Apparatus of claim 1 including a plurality ofmanually operable selector switches, each having a separate contactconnected to each chord switch, a multi-contact sequence switch, meansconnecting the arm of each selector switch to a separate contact of thesequence switch, means connecting the arm of the sequence switch toground, and electrical means including an on-off switch for operatingthe sequence switch.
 9. Apparatus of claim 8 in which the keys operatingthe melody note switches and the keys operating the chord switches arearranged in the form of a typewriter keyboard and the switch foroperating the sequence switch is operated by the space bar of thetypewriter keyboard.
 10. Apparatus of claim 1 in which the signal sourcefor the melody note switches is ground, the two-input gates are norgates, and the reset output of each reset-set flip-flop is connectedwith the other input of the plurality of two-input gates equal to thenumber of melody notes.
 11. Apparatus of claim 1 in which the signalsource for the melody note switches is a voltage source, the twoinputgates are and gates, and the set output of each resetset flip-flop isconnected with the other input of the plurality of two-input gates equalto the number of melody notes.